Vacuum tube for heavy currents



May`l, 1934. H. M. FREEMAN VACUUM TUBE FOR HEAVY CURRENTS Original FiledMarch 29, 1924 nnnnv llllllllll 1.

-s u. n im ...i s

AT'TORNEY Patented May 1, 1934 UNITED sTATEs PATENT OFFICE VACUUM TUBEFOR HEAVY CURRENTS Original applicationMarch 29, 1924, Serial'No.702,716. Divided and` this application May 28,

19h30, Serial No. 456,345

12 Claims. (Cl. Z50-27.5)

This application is a division of application Serial No. 702,716, filedMarchv 29, 1924, and assigned to Westinghouse Electric 8a ManufacturingCompany.

This invention relates to vacuum tube devices of the type used forcontrolling space currents.

It is an object of the invention to produce a device of the classdescribed which can convey a greater space current for a given size ofdevice than has been possible with devices of this class heretofore.

It is a further object of the invention to provide a device in which theheat developed at the anode may be removed by means of a stream ofcooling uid.

It is a further object of the invention to provide a device of the classdescribed in which the cathode may be heated by a coil out of electricalcontact therewith, the heating being accomplished by thermal conduction.

It is a further object of the invention to provide a heating device forthe cathode which can be readily renewed when necessary.

It is a further object of the invention to provide means for minimizingthe escape of heat, from the heating coil, into the surroundingatmosphere.

It is a further object of the invention to so arrange the several partsof the device that a cornpact apparatus is produced without reducing thesize of the electrode surfaces.

vOther objects of the invention and details of the construction will bebetter understood from the following description and the accompanyingdrawing in which;

Figure 1 is a central vertical sectional view of one form of the device.

Fig. 2 is a cross-sectional view on lines II--II of Fig. 1.

The device includes a glass envelope or container 1, which, preferably,is highly evacuated, but the device may still be operated with improvedresults when there is gas remaining within the envelope.

The anode consists of a coil 2 of metal. Copper, silver, or other goodthermal conductor, may be used. Each end of this ycoil passes throughthe glass envelope, as indicated at 3 and 4. A suitable seal between themetal tubing and the glass is made at each of these ends, in order thatthe vacuum within the envelope may be preserved.

The anode is surrounded by any convenient form of grid. Preferably, thegrid is a helix 5, which is supported by a standard 6, welded to eachturn of the helix. The standard extends through the envelope at 'l andserves as a conductor by means of which potentials may be applied tothegrid.

The cathode consists of a cylindrical plate 8,

of a metal that is adapted to withstand high temperatures, such astungsten or platinum. The inner surface of the plate 8 is preferablycoated with a material that will emit electrons abundantly when theplate is hot. A mixture of the oxides of barium and strontium servesthis purpose well, but other coatings of a high emission power may be`used. The cylindrical plate may be supported by a standard 10, whichalso serves as a lead or conductor, or it may be supported in other waysas described below, and the lead 10 will then serve only as a conductor.

Concentric with the cylindrical cathode, is a heating coil 11. In theform shown in Figure 1, this coil is outside of the container 1.

Escape of heat from the coil 11 into the outer atmosphere is preventedor minimized by a covering 14 of heat-insulating material. Preferably,this covering andthe coil ll are made to constitute a single unit whichcan be slipped onto the tube from the small end and will be stopped inthe proper position by the enlargement at the upper end of the tube.

When current is passed through the coill 11 to heat it, heat will flowthrough the glass wall 13 and raise the temperature of the metalliccylinder 8. The emission of electrons f' om the coated inner surface ofthis cylinder will thus be increased. The heat is constrained to passthrough the-glass wall instead of into the surrounding atmosphere by theheat insulation 14.

The cathode 8, preferably ts closely against the inner face of thiscylinder. Any of the usual methods for obtaining a close union betweenthe metallic cylinder 8 and the glass cylinder 13 may be followed. Forexample, the inner surface of the glass may be silvered and a platinumlm electro-chemically deposited on the silver. A tungsten cathode may besealed directly to the inner surface of the glass in the same way thattungsten wire is sealed into the glass when making the usual connectionsfor vacuum devices. The barium and strontiumv salts, or other coatingmaterial, may be applied tothe cathode after it is in place.

In the operation of the device, current, which may be either direct oralternating, is supplied to the coil 11 to heat it. The coil heats thecathode and so produces electron emission. A difference of potentialbetween the cathode and the anode may be supplied by means of the lead10 and an external part of the coiled tube, vvhlc: causes a spacecurrent from Ythe anode 2 to the cathode 8. The bombardment of the anodeby the electrons constituting this space current heats the anode', butheatfis rapidly removed therefrom by the stream of water or othercoolinguid flowing through the coiled anode.,

if the container l. is highly exhausted, the space current is made upWholly oi the electron stream, but if gas be present, ions also willtaire part in the space current. A much larger current may be carried inthe latter case'and a much greater quantity of heat Will beliberated-'lat the anode, but, because oi the provision for cooling theanode with a stream of fluid, the device will transmit large amounts ofpower Without the necessity of building it in prohibitive sizes.

It Will be evident to those skilled in the art that many variations ofstructure may be made without departing from the spirit of thisinvention. No limitations except those necessitated by the prior art orexpressed by the claims is intended. Y

What is claimed is:

l. An electrical discharge device including an envelope having acylindrical Wall having closed ends, an anode,iand a cathode, saidcathode comprising a coating of electron emittingY material on theinterior of said wall, heat producing means and means for minimizingheat dissipation from the external surface of said cylindrical wall.

2. n electrical discharge device including an envelope in the form of acylindrical' wall having closed ends, an anode, a cathode, said cathodecomprising a coating of the electron emitting materialV on the-interiorof said Wall, aheater coil on the exterior of said wall, and means forminimizing heat dissipation from the external surface of said envelope.

3. An electrical discharge device including an envelope in the form of acylindrical-Wall having closed ends, an anode, a cathode, said cathodecomprising a coating of electron emitting material on the interior ofsaid Wall, a heater coil on the exterior of said Wall, and means forminimizing heat dissipation from the external surface of said envelope,said means comprising heat insulating material surrounding said heatercoil.

4. An electrical discharge device including an envelope having a curvedouter Wall, an anode positioned inside said Wall, and a cathode, saidcathode comprising an electron emitting material coated on the concaveinterior of said outer Wall.

5. An electrical discharge device comprising an anode and a cathodeconsisting of a chamber coated on its interior walls with material whichemits electrons freely when heated and means on the exterior Wall ofsaid chamber for maintaining it at an elevated temperature, at least aportion of said anode being surrounded by said cathode.

6. An electrical discharge device including an envelope lin the form ofa cylindrical Wall having closed ends, an anode and a cathode withinsaid cylindrical wall said cathode comprising electron emitting materialadjacent an inner portion of said cylindrical Wall and heat producingmeans on the exterior of said Wall in thermal conducting relation withsaid cathode.

'i'. An electricalldischarge device including an envelope in the formofa cylindrical wail having closed ends, Yan anode and a cathode withinsaid cylindrical YWall said cathode comprising electron emittingmaterial adjacent an inner porn tion of said cylindrical Wall, heatproducing means on the exterior of said wall in thermal V'conductingrelation with said cathode and means Vfor heat dissipation from theexternal surface of said envelope.

3. An electrical discharge device including an envelope, an anode withinsaid envelope, cooling means for said anode, a cathode Within saidenvelope, heating means exterior to and surrounding saidl envelope inthermal conducting relationship with said cathode, and means covering alarge portion of the exterior of said envelope and greatly minimizingthe heat dissi-- pation from the exterior of the device into the outeratmosphere.

9. An electrical discharge devicehaving an anode and a cathodecomprising an electrical discharge chamber coated on its concaveinterior walls with material which emits electrons freely when heated,means for heating said cathode and means for substantiallyminimizingheat dissipation from the external surface of said electrical dischargechamber.

l0. An electrical'discharge device having an anode and a cathodecomprising a wall enclosing an electron-emissive surface, said Wallhaving a convex external surface, electron emitting material on an innerwall of said convex external Wall, means for heating said cathode, andmeans surrounding the convex external surface of said Wall forsubstantially minimizing heat dissipation from said external convexsurface.

li. An electrical discharge device having an anode and a cathodecomprising an electrical discharge chamber coated on its concaveinterior Walls with material which emits electrons freely means forsubstantially minimizing heat dissipation from the external convexsurface of said

